The preparation of chemical and topographic variations on the nano- and micrometer scale are, i.a., of great technical interest for usages in the areas of refractive and diffractive optics, the selection of molecularly important length scales in the cellular adhesion and the bonding of individual molecules on boundary surfaces. This is true in particular for gradual changes of the topography and chemical properties of a surface.
The production of molecularly well-defined gradients offers, e.g., the possibility of investigating directionally controlled processes such as the cell movement that requires external chemical gradients. In particular in the area of cellular haptotaxis chemical gradients with molecular precision are desirable for investigating biological reactions qualitatively and quantitatively in detail. Efimenko and Genzer ((Adv. Mater. 13, 2001), 1560-1563) have shown that a fine positioning of the graft density of molecules on surfaces is possible by the creation of mechanically assembled monolayers (MAMs). MAMs are structures that are produced by a combination of self-assembly, mechanical stretching of a PDMS carrier and molecular diffusion. The method for the production of these MAMs is relatively complex due to the incorporation of a mechanical step and furthermore only suitable for flexible carriers and not for rigid substrates such as, e.g., glass, metal, silicon compounds, etc. Another disadvantage is the fact that a regulation of molecule-molecule distance by mechanical stretching of a substrate is not possible since the clustering of individual molecules cannot be substantially limited.
Accordingly, the present invention has the object of providing an improved, simple and versatile method with which extensive variations in size or distance can be so precisely adjusted in nanostructure patterns on surfaces that defined gradient surfaces are obtained.
This object was achieved in accordance with the invention by a further development of the micellar nanolithography (see, e.g., EP 1 027 157). In the micellar nanolithography a micellar solution of a block copolymer is deposited onto a substrate, e.g., by immersion coating, and, given suitable conditions on the surface, forms an ordered film structure of chemically different polymer domains, depending, i.a., on the type, molecular weight and concentration of the block copolymer. The micelles in the solution can be charged with inorganic salts that can be reduced to inorganic nanoparticles after the deposition with the polymer film. It was now established in accordance with the invention that the lateral separation length of said polymer domains and therewith also of the resulting nanoparticles as well as the size of these nanoparticles can be so precisely adjusted in an extensive area by different measures that nanostructured surfaces with desired gradients of distance and/or size can be created.
Thus, the present invention has as subject matter methods for the extensive variation of sizes or distances in patterns of nanostructures on a substrate.